(a) Field of the Invention
The present invention relates to a wavelength allocation method and a wavelength allocation device, and particularly relates to a wavelength allocation device using a 3R wavelength converter having a limited wavelength conversion range and a wavelength allocation method thereof.
(b) Description of the Related Art
In the high speed optical communication field, a wavelength division multiplexing (WDM) method using optical channels is used to transmit a large amount of data through a single optical fiber.
It is predicted that an optical communication network will be developed from a linear or circular network using a fixed line to an all-transmission network in which a network is dynamically configured by changing an optical channel path.
Particularly, a backbone network will become a mesh-type network based on an optical cross connector (OXC) for reconfiguring lines of each node.
In the mesh type of network in the WDM method, it is required to satisfy a wavelength consecutive condition in which wavelengths of an input channel and an output channel are the same.
A wavelength converter is used to satisfy the wavelength consecutive condition, and research results have been published showing that network efficiency is greatly improved by using a lesser number of wavelength converters compared to the number of optical channels for each node.
However, in the mesh type network in the WDM method, since there is a limit in transmission distance due to quality deterioration caused while an optical signal is transmitted, it is required to consider the wavelength consecutive condition and the quality deterioration of the optical signal.
When an optical signal path is set to be a path that is greater than a signal impairment threshold (SIT), which is a maximum distance for guaranteeing transmission quality, it is required to perform three R functions including Re-amplification, Re-shaping, and Re-timing (hereinafter, referred to as “3R regeneration”) for the optical signal.
In a dynamic WDM network, it is required to fully accept requests for optical path generation, and therefore it is important to not waste resources more than needed when an individual optical path is set.
A 3R wavelength converter performs the 3R function, and converts a predetermined wavelength channel to another wavelength channel. Sine the 3R wavelength converter is expensive, it may not be formed for all the wavelength channels at each node.
Accordingly, in the WDM network, the 3R wavelength converting function is provided to a predetermined node, or the number of 3R wavelength converters is limited, and this will be referred to as a limited wavelength converting function.
It may be wasteful to provide a 3R wavelength converter for performing full wavelength conversion in the WDM network, since the number of wavelengths applied to one link is rapidly increased.
A conventional WDM network having the limited wavelength conversion function sets an assumption of a wavelength conversion condition for performing the wavelength converting function for all the wavelength channels at a predetermined node, or sets an assumption of a wavelength conversion condition performing the limited wavelength converting function at all the nodes.
That is, the limited wavelength conversion condition has been studied only in relation to the wavelength converter. In addition, it has been studied assuming that each wavelength converter may perform the full wavelength conversion.
However, since a maximum transmission distance of the optical signal is limited in the actual WDM network, it is required to consider the wavelength conversion function and the 3R functions.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.